#include <bits/stdc++.h>
#include <atcoder/all>
#define rep(i, n) for (int i = 0; i < n; i++)
#define ll long long
using namespace atcoder;
using namespace std;
#define mint modint998244353
int main()
{
    int n;
    cin >> n;
    vector<mint> a(n);
    rep(i, n)
    {
        int x;
        cin >> x;
        a[i] = x;
    }
    vector<mint> t(n);
    t[0] = 1;
    for (int i = 1; i < n; i++)
        t[i] = 2 * t[i - 1];
    mint ans = 0;
    rep(i, n) ans += (t[n - 1 - i] - t[i]) * a[i];
    cout << ans.val() << endl;
    return 0;
}